1. Field of the Invention
The present invention relates to a method for determining an operating state of elements of a transmission, and more particularly, to a technology of determining connection and disconnection of elements, such as a clutch and a brake, of a transmission in a hybrid vehicle which can implement continuous shifting.
2. Description of Related Art
In the related art, connection and disconnection of elements in automatic transmissions are determined on the basis of a signal detected by a pressure switch.
That is, the pressure switch is disposed in a channel of a valve body which is connected to a corresponding clutch or a brake, such that when pressure above a predetermined level is applied to the pressure switch, it is determined that the element is connected in the channel, or if not, it is determined that the element is disconnected.
However, the method of using the pressure switch, as described above, requires a number of parts and increases the volume and weight of the valve body and the cost, such that it is preferable to be able to determine the operating state of the elements even without using the pressure switch described above.
In the methods of determining the operating state of elements, without depending on the signal from the pressure switch, there is a method of determining connection and disconnection of the elements by comparing the input speed and the output speed of an automatic transmission, but it can be used only for a constant transmission gear ratio, such as an automatic transmission.
A transmission that can implement a fixed stage mode with a constant transmission gear ratio and a power split mode is used for hybrid vehicles, in which although it is possible to determining the operating states of the elements by comparing input/output speeds of the transmission in the fixed stage mode with a constant transmission gear ratio, continuous shifting is implemented by two motors in the power split mode, such that it is impossible to determine the operating states of the element only by simply comparing the input/output speeds of the transmission, because the transmission gear ratio is not constant.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.